While 2017 promises to spotlight the issue of power for the people, it is also stirring up another debate — power for the data center. The two prevailing parties —Alternating Current (AC) voltage and Direct Current (DC) voltage —have been sounding off in recent years, deliberating over whether DC distribution offers enough benefit to instigate a departure from customary AC practice.
But the potential for DC power to positively impact the data center environment is far more than an empty campaign promise. Regardless of party lines, the DC option is gaining momentum among data center operators concerned about power consumption and efficiency in their facilities, yet unwilling to sacrifice reliability.
Although DC is native to virtually all power electronics, for more than 100 years, AC has been the standard for electronic transmission, in part because that is what the utilities provide. Yet modern-day servers, large numbers of electric motors, batteries, ships and airplanes still operate on DC power. Now, as utility costs continue to soar and operators seek greater efficiency, the benefits afforded by DC distribution are prompting an increasing number of data center decision-makers to take note.
One of the primary advantages of DC power is that it eliminates the need for multiple power conversions, which in turn produces sizeable gains in efficiency. In the traditional electrical distribution scheme utilized by the majority of today’s data centers, AC power must first be stepped down from the grid so it can be routed safely in building equipment. Then the lower-voltage AC has to be converted back to DC so it can transfer to uninterruptable power systems (UPSs) and power distribution units (PDUs), before it is converted yet again to AC so it can safely travel over the wires in the building. Then it gets converted back to DC once more. That’s five conversions that must take place.
Yet by converting grid AC to medium-voltage DC at the door of a data center, or converting stepped-down AC to DC at the last possible moment, a facility can shave 10 to 20 percent or more off their utility bills, according to General Electric Several other studies corroborate those findings, including a project conducted by the Lawrence Berkeley National Laboratory that concluded DC produced a 7 percent energy savings over top-notch AC technologies.
Of even greater value to some data center operators is the savings that DC can deliver in real estate; DC data centers require 25 percent to 40 percent less square footage than their AC counterparts, largely because computer equipment can connect directly to backup batteries.
Even Congress weighed in on the belief that traditional distribution practices may have become antiquated, introducing the Energy Efficiency Improvement Act in 2014 and expanding the TENANT STAR certification in 2015 which seeks to forge a new evolution of commercial data center energy efficiency practices. Although applicable only to federally operated data centers, the act is expected to impact the mission-critical facility industry as a whole.
Deploying DC power in modern data centers is more than just a concept. Software giant SAP invested $128,000 to retrofit its Palo Alto, California, data center into a DC facility —slashing energy bills by $24,000 per year as a result. And in 2014, Quality Technology Services (QTS) migrated to DC power distribution for enhanced energy efficiency, unveiling a 360,000-square-foot data center in Princeton, N.J., that supports 57,000 solar panels throughout a 50-acre solar farm.
Driven by the opportunity to turn small efficiency gains into tremendous cost savings has made some data center operators willing to buck the status quo and pursue the less conventional DC approach in their facilities. Ultimately though, the value of DC versus AC will likely come down to return on investment, with financial resources expected to remain the biggest barrier to widespread adoption of DC power.